Photographic diffusion transfer process



United States Patent 3,232,758 PHOTOGRAPHIC DIFFUSION TRAYSFER PROCESS Colin Holstead and Leslie A. Williams, Harrow, England, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Apr. 11, 1969, Ser. No. 21,151 Claims priority, application Great Britain, Oct. 16, 1959, 35,060/ 59 8 Claims. (Cl. 96-29) This invention relates to photographic processes for producing direct positive images and to materials for use therein.

In photography, most of the layers in which photographic images are found are themselves originally lightsensitive. However, not all photographic layers used for forming images are light-sensitive and the present invention concerns a class of non-light-sensitive layers, namely, those containing development nuclei for silver salts or substances forming development nuclei at a suitable stage in the photographic process or precipitants for silver salts by double decomposition. Such non-lightsensitive layers are used for to form positive silver or silver salt images therein by reaction between the substances in the layers and dissolved silver salts diffusing thereinto from the unexposed areas of contiguous silver halide emulsion layer which has been exposed imagewise and which has been or is being developed to a negative image.

One drawback sometimes encountered in processes of this type is that the positive image produced is of a brownish or other non-acceptable colour.

The present invention provides a sheet material comprising a non-light-sensitive photographic layer containing a silver precipitating agent such as development nuclei, or a substance capable of forming development nuclei with dissolved silver salts, or a precipitant for silver salt, and also containing a compound of the following general formula:

wherein R may be an aliphatic acid acyl group, a sulfonic acid acyl group, benzyl or furfuryl group, R may be hydrogen or a monocyclic acyl group of the benzene series, e.g. phenyl, o-tolyl, o-chloro phenyl etc., and R" Related compounds such as thiosemicarbazide and 1,4- diphenylthiosemicarbazide are not useful for the purposes of our invention since they do not improve the image color when the diffusion transfer process is carried out in their presence.

The invention includes the process of preparing a direct positive image which comprises exposing a photographic silver halide emulsion layer to an object or image, developing a negative image in the exposed layer, and, during or after development, transferring silver halide by diffusion from the unexposed areas of the emulsion layer to a non-light-sensitive image-receiving layer containing development nuclei or a substance capable of forming development nuclei with dissolved silver halide and in effective contact with the emulsion layer, the transfer being effected in the presence of a silver halide solvent and a compound of the above general formula.

By in effective contact, we mean that dissolved silver salts can diffuse from the emulsion layer to the non-lightsensitive layer. There may be an intermediate layer present between the two aforesaid layers which does not hinder the silver salt diffusion, and the two layers may or may not be coated on the same support.

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We have found that the presence of one of the compounds of the present invention has the effect of producing a blacker positive image than would otherwise be produced.

In the process of the invention, the said compound may be present in the receiving layer or in the solution employed for effecting development in the emulsion layer, and the mentioned transfer of silver halide may therefore be carried out by means of the silver halide solvent in contiguity with the said compounds of the invention.

An alkaline solution is used to effect development of the exposed layer and the developing agent may be present in either the emulsion layer or in the alkaline solution or both. A mixture of developing agents may be used, if desired.

The silver halide solvent may be present in the developing solution or the receiving layer and is preferably sodium thiosulphate.

It is preferable to employ an antifoggant to prevent the formation of fog in the exposed emulsion layer and this may be present in either the emulsion layer or in the alkaline solution used to effect development. Any of the well-known nitrogen-containing organic antifoggants may be used and it has been found that benztriazoles are very suitable.

The compounds of the invention are preferably employed in the following concentrations: from 5 to 30 mgs./ sq. metre, when incorporated in the receiving layer; or from 0.05 to 0.5 gram/litre, when incorporated in the developing solution.

A suitablenon-light-sensitive image-receiving layer for use in the present invention comprises a gelatin layer con: taining a substance constituting development nuclei (such as colloidal silver or silver sulphide) or a substance forming development nuclei with dissolved silver salts (such as zinc sulphide), and also containing one of the compounds of the invention. I

Such a layer may be coated on a paper support and contacted in the presence of a silver halide solvent with an exposed and developing emulsion layer which may be coated on a separate support, or may be coated on the same support as the emulsion layer. In the latter case, it is preferable to coat the non-light-sensitive layer on a paper support, then to overcoat this layer with a cornparatively unhardened emulsion layer. After exposure, development and formation of the direct positive image in the non-light-sensitive layer, the exposed and developed unhardened emulsion layer is removed, for example, by washing in warm water.

The following examples illustrate the present invention.

Example 1 A high contrast silver chloride emulsion containing the following constituents is coated on a paper support at the mentioned coating rate:

Grams/ sq. in.

Silver chloride 1.4 Diphenyl iodonium-S-methyl benztriazole 0.063 Hydroquinone 0.28 Gelatin 5.6

The resulting emulsion layer is exposed to a subject such as a document and treated with the following developer:

Water to 1 litre.

During or after development, the exposed emulsion layer containing" developing agent i is squeegee'd for about seconds into contact with an image-receiving sheet comprising a light weight paper support bearing a nucleated layer as follows:

I A Grams/sq. n1.

developed areas of the emulsion layer to an image-receiving layer containing a silver precipitating agent, the

Gelatin g 6.1 Sodium thiosulphate (anh.) 1.4 7 Titanium dioxide 0.63

Colloidal silver sulphide 0.0027 l-benzylthiosemicarbazide 0.01

After separating the layer and the sheet, a positive image of a neutral blue-black colour was obtained on the receiving sheet.

Similar results were obtained when employing, instead of l-benzylthiosemicarbazide the following compounds in the specified amounts:

Grams/ sq. m.

Methyl [-1-butyroyldithiocarbazinate 0.02

Methyl ,fi benzoyldithiocarbazinate 0.02

l-benzoylthiosemicarbazide 0.02

' Example 2 The procedure of Example 1 was repeated with the exception that methyl fl-butyroyldithiocarbazinate was employed in the developer (0.05 gram/litre) and there was no toning agent in the receiving sheet. A positive image of a neutral-black colour was obtained in the receiving sheet.

Similar results were obtained when employing, instead of methyl f3bratyroyldithiocarbazinate the following compounds in the specified amounts:

Gram/litre l-p-toluenesulphonylthiosemicarbazide 0.1 Methyl B-benzoyldithiocarbazinate 0.05 1-(2'-furfuryl)thiosemicarbazide' 0.05

The compounds referred to in the above examples have the following references or preparations.

J.C.S., 1163 (.1949).

Molar quantities of p-toluenesulphonyl chloride and thiosemicarbazide were reacted together in pyridine at room temperature. The product was recrystallized from ethanol and has a melting point of 212 C.

Methyl B-butyroyldithiocarbazinate British Patent No. 571,174. Methyl B-benzoyldithiocarbazinate I. prakt. Chem. (2), 93, 50.

What we claim is: v

1. A process for preparing a photographic image by the diffusion transfer process comprising developing a latent image in a photographic silver halide emulsion, transferring the silver halide by diffusion from the untransfer being effected in contiguity with a silver halide solvent and a compound of the class consisting of l-benzylthiosemicarbazide, methyl fi-butyroyldithiocarbazinate, methyl fl-benzoyldithiocarbazinate, l-benzoylthiosemicarbazide, 1-p-toluenesulphonylthiosemicarbazide, and 1-(2-furfuryl)thiosemicarbazide.

2. A process for preparing a photographic image by the diffusion transfer process comprising developing a latent image'in a photographic silver halide emulsion, transferring the sliver halide by diifusion from the undeveloped areas of the emulsion layer to an image-receiving layer containing a silver precipitating agent, the transfer being elfected in contiguity with a silver halide solvent and 1-benzylthiosemicarbazide.

3. A process for preparing a photographic image by the diffusion transfer process comprising developing a latent image in a photographic silver halide emulsion, transferring the silver halide by diffusion from the un developed areasof the emulsion layer to an image-receiving layer containing a silver precipitating agent, the transfer being effected in contiguity with a silver halide solvent and methyl B-butyroyldithiocarbazinate.

4.'A process for preparing a photographic image by the diffusion transfer process comprising developing a latent image in a photographic silver halide emulsion,

transferring the silver halide by diffusion from the undeveloped areas of the emulsion layer to an image-receiving layer containing a silver precipitating agent, the transfer being effected in contiguity with a silver halide solvent and methyl ,B-benzoyldithiocarbazinate.

5. A process for preparing a photographic image by i the diffusion transfer process comprising developing a latent image in a photographic silver halide emulsion, transferring the silver halide by dillusion from the undeveloped areas of the emulsion layer to an image-receiving layer containing a silver precipitating agent, the transfer being effected in contiguity with a silver halide solvent and l-benzoylthiosemicarbazide.

6. A process for preparing a photographic image by the diffusion transfer process comprising developing a latent image in a photographic silver halide emulsion, transferring the silver halide by dilfusion from the undeveloped areas of the emulsion layer to an image-receiving layer containing a silver precipitating agent, the transfer being effected in contiguity with a silver halide solvent and l-ptoluenesulphonylthiosemicarbazide.

'7. The process of claim 1 wherein the designated compound is present in the developer solution during the transfer step.

8. The process of claim 1 wherein the designated compound is present in the image-receiving layer during the transfer step.

7 7 References Cited by the Examiner UNITED STATES PATENTS 2,423,767 7/1947 Fry 61: al. 96-52 2,699,393 .1/1955 Weyde 9629 3,017,270 1/1962 Tregillus et al 9629 FOREIGN PATENTS 511,060 5/1952 Belgium. 542,151 11/1955 Belgium.

NORMAN G. TORCHIN, Primary Examiner. 

1. A PROCESS FOR PREPARING A PHOTOGRAPIC IMAGE BY THE DIFFUSION TRANSFER PROCESS COMPRISIG DEVELOPING A LATEN IMAGE IN A PHOTOGRAPHIC SILVER HALIDE EMULSION. TRANSFERRING THE SILVER HALIDE BY DIFFUSION FROM THE UNDEVELOPED AREAS OF THE EMULSION LAYER TO AN IMAGE-RECEIVING LAYER CONTAINING A SILVER PRECIPITATING AGENT, THE TRANSFER BEING EFFECTED IN CONTIGUITY WITH A SILVER HALIDE SOLVENT AND A COMPOUND OF THE CLASS CONSISTING OF 1-BENZLTHIOSEMICARBAZIDE, METHYL B-BENZOYLDITHIOCARBAZINATE, METHYL B-BENZOYLDITHIOCARBAZINATE, 1-BENZOYLITHIOSEMICARBAZIDE, 1-P-TOLUENESULPHONYLTHIOSEMICARBAZIDE, AND 1-(2''-FURFURYL)THIOSEMICARBAZIDE. 